Food condition maintaining device

ABSTRACT

The inventive food holding apparatus comprises a holding area that accommodates food and warms the food with heat radiated by a bottom surface and with warm convection air. Part of the convection air forms an air curtain having a Bernoulli effect that removes excess moisture from the external surface of the food and maintains the food in a warm, crisp condition. The apparatus conditions food to attain a biologically safe noncooking temperature and to retain its freshly cooked texture and internal moisture for more than two hours. This lets restaurants serve the food longer to its customers, allowing efficient batch cooking and significantly decreasing food waste.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. patentapplication Ser. No. 13/423,003 filed Mar. 16, 2012, now U.S. Pat. No.9,027,470, which claims priority to U.S. Provisional Application No.61/465,359, filed Mar. 18, 2011, the disclosures of which are explicitlyincorporated by reference herein.

BACKGROUND ART

Restaurants use food-holding cabinets to keep fried food (e.g., frenchfries, fried onions, and hash browns), rethermalized fried food (e.g.,frozen pre-fried french fries that are baked in a convection ovenshortly before serving), and non-fried food (e.g., bread) hot and crisplonger before serving the food to customers.

The typical frying process includes quickly heating food in a deep fryerat around and above 350 degrees F. This frying process quickly removesmoisture from the surface of the fried food, giving it a hot, crispappearance. The typical rethermalizing process includes baking frozenpre-cooked food in a baking oven, such as a convection oven, at aroundand above 350 degrees F.

Fried food quickly deteriorates once removed from its primary cookingsource. The typical hold time for fried food is between 5 and 7 minutes.Rethermalized fried food typically has a hold time of only 3 to 5minutes because its crisp surface (which acts as a barrier to loss offood heat and internal moisture) is thinner than that of recently friedfood. Thereafter, the food becomes soft and develops a greasyappearance. Internal food moisture quickly creeps towards and softensthe outer surface of the food, leading to many customer complaints aboutgreasy and old food.

Patents such as U.S. Pat. Nos. 4,499,818; 6,114,659; and 6,261,621describe the use of radiant heat and/or convection air to keep food hotand crisp. In 1985, U.S. Pat. No. 4,499,818 described the original ideaof improving the holding time of fried food. U.S. Pat. No. 6,261,621described a fried food-holding area having recirculating hot air forcedon and about fried food items, a lower heater, and an upper heater madeof overhead heating lamps. Many tests have shown that overhead heatinglamps in any application cause fried food to quickly develop a moistouter surface. U.S. Pat. No. 6,114,659 described a food-holding binhaving a base for holding food to be warmed. The base had first andsecond opposed edges, third and fourth opposed edges, and first andsecond end walls disposed at the first and second opposed edges of thebase. Regions above the base and along the third and fourth opposededges between the first and second end walls were substantially open toambient atmosphere.

SUMMARY

Embodiments of the inventive holding apparatus keep the interior of foodheld in a holding area warm and moist and the exterior surface of thefood warm and crisp by applying to the food a combination of radiantheat, flowing warm convection air, a warm air curtain, and a Bernoullieffect. An air flow assembly heats a bottom surface of the holding area,which radiates heat to the food, and generates a flow of warm convectionair that the assembly applies to and about the food. The air flowassembly creates from a portion of the flow of warm convection air anair curtain that flows within the holding area apart from the food togenerate negative pressure through a Bernoulli effect, which helps toevaporate and remove excess moisture from the food surface. An openingin the holding area allows operators of restaurants and kitchens easyaccess to the food. Tests show that the embodiments can extend theserviceable holding time of food to more than two hours, lettingrestaurants serve food held by the apparatus for longer times to theircustomers and benefit from efficiently cooking food in batches and fromsignificantly decreasing the waste of food.

One aspect of the invention is the development of a holding system thatmaintains warm, internally moist, crisp food with a balanced combinationof one or more of radiant heat, warm convection air, a warm air curtain,and a Bernoulli effect.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a perspective view of the food-holding apparatus.

FIG. 2 is a sectional view of the apparatus, taken on cutting planelines 1-1 of FIG. 1.

FIG. 3 is a sectional view of the apparatus, taken on cutting planelines 2-2 of FIG. 1, illustrating a recirculating air flow.

FIG. 4 is a sectional view of the apparatus, taken on cutting planelines 3-3 of FIG. 1.

FIG. 5 is a perspective view of the food-holding apparatus with a singlefood bin.

FIG. 6 is a perspective view of the food-holding apparatus in adouble-stacked single bin configuration.

FIG. 7 is a sectional view of the control panel.

FIG. 8 is a sectional view of the food-holding apparatus with thecontrol panel detached from the apparatus.

FIG. 9 is an exploded view of FIG. 1.

FIG. 10 is a sectional view of the apparatus depicting use of a shieldfor holding externally moist food in the apparatus.

FIG. 11 is an exploded view of the apparatus depicting use of a food binchute.

FIG. 12 is a perspective view of the apparatus having a lid.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the drawings representembodiments of the present invention, the drawings are not necessarilyto scale and certain features may be exaggerated in order to betterillustrate and explain the present invention. The exemplifications setout herein illustrate embodiments of the invention, in several forms,and such exemplifications are not to be construed as limiting the scopeof the invention in any manner.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments described and disclosed below are not intended to beexhaustive or to limit the invention to the precise forms disclosed inthe following detailed description. Rather, the embodiments are chosenand described so that others skilled in the art may utilize theirteachings.

Various embodiments of apparatus 10 described here apply to holding area13 a balanced combination of radiant heat, warm air convection,insulating warm air curtain 61 (a flow of coherent air), and a negativepressure region from a Bernoulli effect resulting from warm air curtain61 to quickly stop food in holding area 13 from cooking and to hold thefood at a biologically safe, satisfying temperature (from about 140degrees F. to about 190 degrees F., more particularly from about 155degrees F. to about 175 degrees F.). In so doing, the apparatusmaintains the freshly cooked texture and internal moisture of the foodfor at least two hours. Food-holding temperatures below 140 degrees F.are biologically unsafe, and above 190 degrees F. typically overcook andruin food. Radiant heat and warm air convection maintain food at abiologically safe temperature without overcooking it. Warm air curtain61 thermally insulates holding area 13, creates negative pressure byvirtue of a Bernoulli effect that lowers the static air pressure aroundfood items in holding area 13, and removes moisture from holding area13. Warm air convection and the lowered static air pressure evaporateand remove excess moisture from the food surface, conditioning the foodto retain its freshly cooked texture and internal moisture. Foodsuccessfully maintained by this apparatus includes crisp fried food(such as french fries, chicken strips, onion rings, popcorn shrimp, andhash brown potatoes), rethermalized fried food (such as frozen pre-friedfrench fries baked in a convection oven), baked food (such as bread,buns, biscuits, rolls, egg rolls, croutons, cookies, and other bakedfood). Inedible objects successfully maintained by this apparatusinclude plates, cups, napkins, eating utensils (such as knives, forks,and spoons), and drinking glasses.

FIGS. 1 through 4 show an embodiment of holding apparatus 10. Thematerial of apparatus 10 may be corrosion-resistant metal (such asstainless steel), ceramic, glass, stone, minerals, brick, or any othercorrosion-resistant material able to withstand operating temperatures ofapparatus 10 and salt from the food. To resist corrosion, the materialmay be stainless steel type 304 in one embodiment, and stainless steeltype 316 in another embodiment. Apparatus 10 may be configured in anyshape (such as circular, oval, triangular, or globular), FIGS. 1 through4 showing apparatus 10 as having a rectangular shape.

Removable food holder 20, for holding food and inedible objects, nestswithin holding area 13 of apparatus 10. Food holder 20 supports food,admits radiant heat and warm convection air to the food, and providesconditions that facilitate creation of air curtain 61. Food holder 20may be made of metal, plastic, ceramic, brick, glass, wood, paper,stone, minerals, or any other material capable of withstanding theoperating temperatures of holding area 13. Food holder 20 may beconfigured in any shape and size compatible with that of holding area13, in one embodiment as a circular food plate (not shown), and inanother embodiment as rectangular food bin 21. An embodiment of food bin21 is open at the top and comprises a bottom base section 22 and atleast one upright wall 23. One embodiment of food bin 21 has an optionalhandle 24 that facilitates safe removal of food bin 21 from holding area13.

One embodiment of food holder 20 includes removable top shield 26 whichradiates heat received from warm convection air and from warm aircurtain 61 to food having a desirably moist external surface (such assauteed onions; scrambled eggs; cooked fruit, vegetables, and meat; andcasseroles) held in food holder 20 and shields the food from the dryingBernoulli effect of warm air curtain 61. Shield 26 may be made of anymaterial (such as stainless steel, plastic, ceramic, glass, brick,stone, or minerals) able to withstand the operating temperatures ofholding area 13 and to radiate an amount of heat sufficient to maintainfood held in food holder 20 at a satisfying, biologically safetemperature without overcooking the food. An embodiment of shield 26contains apertures that let excess moisture escape from food holder 20.In one embodiment, one shield 26 is positioned atop each food bin 21. Inanother embodiment (shown in FIG. 10), edges of shield 26 slide intoindentations 65 of side wall 36 of food-holding area 13 such that oneshield 26 is positioned near, but above, multiple food bins 21 nestedwithin holding area 13, allowing workers easy access to food bins 21.

Apparatus 10 comprises air flow assembly 79 that includes heater 68, airblower 70, and chamber 12 which defines air channel 74. Air flowassembly 79 produces and recirculates a flow of warm air through airchannel 74, which has four portions (shown in FIG. 3)—holding portion 75for holding and maintaining food; blower directing portion 76 forguiding air flow from holding portion 75; base portion 77 positionedbelow holding portion 75 for guiding air flow from blower directingportion 76 and for radiating heat received from the warm air flow toholding portion 75; and air exhaust portion 78 for receiving air fromthe base portion and for guiding air to holding portion 75. In oneembodiment, air flow assembly includes insulating external cavity wall73, closed at the top and sides, that encloses the bottom and lateralperiphery of air channel 74, and fluidly communicates with air channel74 air stored in cavity wall 73 and warmed by the recirculating warmair. Air blower 70, located near or in blower directing portion 76,impels air flow from blower directing portion 76 through heater 68,located in base portion 77, into base portion 77 to create a flow ofwarm convection air that recirculates through air channel 74.

Apparatus 10 contains at least one holding area 13 that defines airchannel holding portion 75—at its top by top wall 30, at its side byside wall 36, and at its base by base wall 47 (as shown in FIG. 2). Basewall 47 is heated from below by base portion 77 of air channel 74 and inturn radiates heat through removable food holder 20 to the food. Sidewall 36 includes air outlet port 91 that directs the flow of warm aironto and about cooked food and other items held in holding area 13 tocondition the food and items, and that is configured to create a warminsulating air curtain flowing across holding area 13; and includes airinlet port 90 spaced apart from, positioned opposite to, and alignedwith air outlet port 91, for releasing air and moisture from holdingarea 13, and for developing air curtain 61 by drawing and guiding asubstantially laminar flow of air from air outlet port 90. Each air port90, 91 is designed to promote laminar air flow and has in one embodimentfrom about 20 to about 30 apertures 66 having a height of from about 1to about 2 inches and a width of from about 0.15 to about 0.25 inches.The length of each air port 90, 91 is positioned, in one embodiment (asshown in FIG. 3) horizontally near a top edge of side wall 36, and inanother embodiment vertically near a lateral edge of side wall 36. Airports 90, 91 are spaced apart: in one embodiment (shown in FIG. 5) byfrom about 6 to about 8 inches to accommodate one food bin 21 in holdingarea 13; in another embodiment (shown in FIG. 1) by from about 15 toabout 18 inches to accommodate one or two food bins 21; and in yetanother embodiment by from about 18 to about 24 inches to accommodateone, two, or three food bins 21. In various embodiments, the food binsrange in height from about 2.5 inches to about 8 inches and in widthfrom about 5 inches to about 22 inches. Top wall 30 thermally insulatesholding area 13 and, by preventing upward extension of air curtain 61,guides laminar flow of air curtain 61 between air ports 90, 91 tomaximize the drying Bernoulli effect of air curtain 61.

In one embodiment, top wall 30 of holding area 13 is innermost section32 of top cavity wall 31; side wall 36 includes both innermost section38 of side cavity wall 37 and innermost section 42 of air outlet doublecavity wall 41; and base wall 47 includes innermost section 49 of basedouble cavity wall 48. Each cavity wall 31, 37 includes a pair of wallsections spaced apart by an insulating cavity comprised of: top cavitywall 31 comprising innermost wall section 32, top cavity 33, externalwall section 34, and closure 56 that joins adjacent innermost 32 andexternal 34 sections to enclose cavity 33 and prevent heat loss; andside cavity wall 37 comprising innermost wall section 38, side cavity39, external wall section 40, and closure 56 that joins the top ofadjacent innermost 38 and external 40 wall sections to prevent heatloss. An embodiment of side cavity wall 37 (shown in FIG. 2) has threesegments (shown in FIG. 4): front segment 55, back segment 57, andcontrol panel segment 58 which is positioned opposite air outlet doublecavity wall 41. Air inlet port 90 is located near the top of innermostwall section 38 of control panel segment 58.

Each double cavity wall 41, 48 comprises three wall sections spacedapart by two cavities: air outlet double cavity wall 41 comprisinginnermost wall section 42, air channel cavity 43, middle wall section44, insulating cavity 45, external wall section 46, closed at the top inone embodiment by top cavity wall 31; and base double cavity wall 48comprising innermost wall section 49, air channel cavity 50, middle wallsection 51, insulating cavity 52, external wall section 53, closed atthe sides in one embodiment by side wall 36. Air outlet port 91 islocated in the innermost wall section 42 of the air outlet double cavitywall 41.

Wall cavities 33, 39, 45, and 52 contain an insulating material (such asair, mineral wool, polystyrene beads or granules, or rubber foam) toprevent heat loss from holding area 13 and to lessen the temperature ofexterior surfaces. Side cavity 39 and insulating cavities 45, 52 arecontinuous, allowing stored air warmed by the circulating flow of warmair to move freely within them. External cavity wall 73, in oneembodiment, comprises side cavity wall 37; the external wall section 46,insulating cavity 45, and middle wall section 44 of air outlet doublecavity wall 41; and external wall section 53, insulating cavity 52, andmiddle wall section 51 of base double cavity wall 48. In one embodiment,external wall sections 34,40,46,53 have air venting louvers 19 forreleasing heat and moisture from within food-holding apparatus 10.

At least one opening 15 in holding area 13 provides workers with easyaccess to food held in food holder 20 and facilitates cleaning ofholding area 13. One embodiment of holding area 13 (such as that shownin FIG. 1) having one opening 15 in side cavity wall 37 is furtherdefined by top cover 54 and closure 56. Top cover 54 thermally insulatesholding area 13 and sets the height of opening 15 to admit only foodholders 20 having a height, and holding an amount of food, conducive toformation of a robust warm air curtain 61 flowing above food holders 20and to prevention of introducing food particles into air ports 90,91. Inone embodiment, the distance from the top of food bin 21 to top wall 30of holding area 13 is from about 1 to about 3 inches. Top cover 54 is inone embodiment (shown in FIG. 1) detachably joined to top cavity wall 31by fasteners (such as stubs 62, hooks, snaps, screws, bolts, or Velcro),in another embodiment permanently joined (such as by welding, soldering,or applying adhesive) to top cavity wall 31, in another embodimentdetachably joined to side wall 37 (such as by stubs 62, hooks, snaps,screws, bolts, or Velcro), and in another embodiment permanently joined(such as by welding, soldering, or applying adhesive) to side wall 37.Closure 56, in one embodiment, extends base wall 47 of holding area 13to external section 40 of side cavity wall 37 by joining external 40 andinnermost 38 sections of side cavity wall 37. Holding area 13 has in oneembodiment two openings 15, one in front side 16 of side cavity wall 37and one in the back side of side wall 37; in another embodiment twoopenings 15, one in top cavity wall 31 and one in side cavity wall 37;and in yet another embodiment three openings 15, one in side cavity wall37 of front side 16 of apparatus 10, one in side cavity wall 37 of theback side of apparatus 10, and one in top cavity wall 31.

An embodiment of holding area 13 having opening 15 in top wall 30 isfurther defined by lid 35, which covers the opening to thermallyinsulate holding area 13, to maximize the Bernoulli effect of warm aircurtain 61, and to protect food from the environment. Lid 35 is, in oneembodiment, removable from top wall 30, and in another embodimenthingedly fixed to top wall 30, and in yet another embodiment hingedlyfixed to side wall 36. In one embodiment, lid 35 is entire top wall 30of holding area 13. One embodiment (shown in FIG. 12) of lid 35 has airoutlet vent 92 which lets warm moist air escape from holding area 13,and air inlet vent 93 which lets cool dry air enter into holding area13. The lengths of air vents 92, 93 lie perpendicular to the flow of aircurtain 61 of holding area 13, which in one embodiment extend to withinabout 3 inches of the edge of lid 35, are each about 1 inch wide andangled from about 10 to about 30 degrees relative to the surface of lid35, are positioned such that air outlet vent 92 lies closer then airinlet vent 93 to air outlet port 91 of holding area 13, and arepositioned at about ⅔ the length of air curtain 61 from air outlet port91.

An optional food bin chute 28 reversibly secures food bin 21 toapparatus 10 to help workers safely remove food from food bin 21. Chute28 is joined to a wall (in one embodiment side wall 36, and in anotherembodiment bottom wall 47, and in another embodiment top wall 30, and ina further embodiment external wall section 40 of side cavity wall 37) orclosure 56 of apparatus 10, fixedly in one embodiment by welding, anddetachably in another embodiment (to facilitate cleaning of holding area13) by fasteners (such as pins 29). Chute 28 is positioned horizontallyin one embodiment (shown in FIG. 11), vertically in another embodiment(not shown); outside apparatus 10 in one embodiment (also not shown),and within holding area 13 in another embodiment. Tests show thatpositioning chute 28 outside apparatus 10 results in unsafely hot foodbin handles 24. Chute 28 includes angled brackets, through which foodbin 21 may be inserted into food holding area 13, and in one embodiment(shown in FIG. 9) includes linker 27 for joining the brackets. Forhorizontally positioned chute 28, linker 27 is positioned, in oneembodiment (shown in FIG. 11) at the bottom of chute 28, and in anotherinverted embodiment at the top of chute 28. In one embodiment, linker 27is positioned at the top of the horizontal chute and is elongated tocover and shield desirably moist food held in food bin 21 from dryingdue to the Bernoulli effect of warm air curtain 61.

Apparatus 10 may contain as many holding areas 13 as may be covered bywarm air curtain 61; one embodiment (shown in FIG. 5) having one holdingarea 13, and another embodiment (shown in FIG. 6) having two holdingareas 13. Holding area 13 may contain as many food holders 20 as may fiton base wall 47; one embodiment (shown in FIG. 5) containing one foodbin 21, and another embodiment (shown in FIG. 1) containing two foodbins 21.

To facilitate cleaning and repair of apparatus 10, one embodiment ofexternal wall section 40 of control panel segment 58 of side cavity wall37 is detachably joined (as shown in FIG. 8) to front 16 and back sidesof external wall section 40 of side cavity wall 37 and is joined tocontrol panel segment base 59 positioned within side cavity 39 ofcontrol panel segment 58 above middle wall section 51 of base doublecavity wall 48.

Air blower 70 (such as a cross-flow fan shown in FIG. 7, an axial-flowfan [not shown], or a radial-flow fan [not shown]) operated by attachedair blower motor 71 is positioned above control panel segment base 59.Air blower 70 is detachably joined, in one embodiment to control panelsegment base 59, and in another embodiment to external wall section 40of control panel segment 58. Air blower 70 forces air through adjacentheater 68 (such as a wire heater or a calrod heater), positioned withinair channel cavity 50 of base double cavity wall 48 and supported bycontrol panel segment base 59, to produce a flow of warm convection airin air channel cavity 50. In one embodiment, heater 68 is detachablyjoined to air blower 70. Complementary operational alignment of airblower 70 with heater 68 compensates for any functional asymmetry ineither device to produce a symmetric flow of warm air through airchannel cavity 50.

Air inlet 72 of air blower 70 abuts and receives air 97 from opening 83in base 81 of air funnel 80, positioned within blower directing portion76 of air channel 74, and in one embodiment within side cavity 39 ofcontrol panel segment 58. In one embodiment, blower 70 is joined to base81. Angled side wall 84 of air funnel 80, which in one embodiment isattached to external wall section 40 of control panel segment 58, abutsand directs air flow from air inlet port 90 to opening 83 in funnel base81. One embodiment of air funnel 80 has top wall 85 joined to side wall84. Under standard operating conditions (i.e., conditions favorable toroutine operation of the apparatus), extensions 82 of the funnel base(which are represented by flanges of the base 81 in one embodiment andbrackets attached to the base 81 in another embodiment) downwardlydirected from opening 83 in funnel base 81 restrict the flow of air fromair blower 70 to only air channel cavity 50 of base double cavity wall48. One embodiment of funnel 80 includes optional ultraviolet light 100,for converting air impurities (such as oil droplets, food particles, andbacteria) to harmless fine ash, positioned within interior of the funneland attached to wall 84, 85 or base 81 of air funnel 80 or to externalwall section 40 of control panel segment 58.

Apparatus 10 needs no electrical temperature-regulating device (such asa thermostat or thermocouple) to achieve and maintain a stableperformance after from about 2 to about 3 hours of operation understandard conditions or under adverse conditions having an operatingtemperature within at least 20 degrees F. of the standard operatingtemperature. Air channel 74 dimensions and apertures, insulationmaterial and venting louvers of air cavity wall 73, the air curtain, andfunctionally compatible heater 68 and air blower 70 cooperate to createoperational stability in the absence of a thermostat. For example, anembodiment of apparatus 10 having within base portion 77 of air channel74 a heat displacement factor of from about 2 to about 3 Watts per cubicinch and an air velocity of from about 250 feet per minute to about 800feet per minute, and having within air exhaust portion 78 of air channel74 and air velocity of from about 400 feet per minute to about 800 feetper minute maintains thermal stability over a range of from about 200Watts to about 800 Watts of heat output and over a 20 degree F.variation in room temperature.

One embodiment (such as that shown in FIG. 7) of apparatus 10 includeselectrical controls (such as electrical receptacle 101, power switch102, thermocouple 103, electrical control board 104, power board 105,reset fuse 106, and electrical ground 109). In one embodiment, thecontrols are detachably joined to external wall section 40 of controlpanel segment 58 and are supported by control panel segment base 59.Electrical receptacle 101 admits electric current to apparatus 10. Powerswitch 102 turns the apparatus on and off. Reset fuse 106 protectsapparatus 10 from harmful surges of electrical current. Thermocouple 103controls the air temperature of apparatus 10 by measuring airtemperature and by signaling that measurement to electrical controlboard 104. Control board 104 compares the measured temperature to atemperature set by an operator and signals power board 105 to supply, inone embodiment, heater 68 with an amount of electrical power needed togenerate an amount of heat, and in another embodiment air blower motor71 with an amount of electrical power needed to oscillate at afrequency, needed to achieve the set temperature. Thermocouple 103 ispositioned, in one embodiment, within air funnel 80, and in anotherembodiment within air channel cavity 50 of base double cavity wall 48,and in yet another embodiment within air channel cavity 43 of air outletdouble cavity wall 41. In food holding area 13, maintaining food at adesired temperature of from about 140 degrees F. to about 190 degrees F.(more particularly from about 155 degrees F. to about 175 degrees F.)typically requires at the air outlet port 91 an air temperature of fromabout 225 degrees F. to about 350 degrees F. (more particularly fromabout 265 degrees F. to about 325 degrees F.) and an air velocity offrom about 250 to about 1500 feet per minute (more particularly fromabout 800 to about 1200 feet per minute).

Mechanical thermostat 107 and single-use shut-off fuse 108 are safetydevices that protect apparatus 10 from overheating under destructiveconditions (such as a grease fire) by preventing the flow of electriccurrent to heater 68 and to air blower motor 71. Thermostat 107 is setto operate at a temperature at least 20 degrees F. higher than thehighest standard operating temperature of apparatus 10 measured atthermostat 107. At this set temperature, thermostat 107 is typicallyclosed, making thermostat 107 durable. Thermostat 107 is positioned, inone embodiment within heater 68, and in another embodiment within airchannel cavity 50 of base double cavity wall 48, and in yet anotherembodiment within air channel cavity 43 of air outlet double cavity wall41. Single-use shut-off fuse 108 is positioned within heater 68 and isset to operate at a temperature at least 25 degrees F. higher than theoperating temperature of thermostat 107.

FIG. 3 shows an embodiment of air flow assembly 79 that produces andrecirculates a flow of warm air through apparatus 10. Ranges of airvelocity and air temperature described here apply to an embodiment inwhich air inlet port 90 and oppositely aligned air outlet port 91 ofholding area 13 are spaced apart by from about 12 inches to about 15inches. Increased spacing of air ports 90, 91 requires increased heat,air velocity, or air volume; decreased spacing requires decreased heat,air velocity, or air volume. Air velocity and air volume can be changedby changing the rotation frequency of air blower 70, the size of airports 90, 91, and the structure of air cavities 39, 43, and 50. Theamount of heat can be changed by changing the wattage of heater 68.

Under standard operating conditions, air circulates through fourportions of air channel 74 of air flow assembly 79 (as shown in FIGS. 3and 10) blower directing portion 76, base portion 77, air exhaustportion 78, and holding portion 75. Air blower 70 creates a slightlynegative air pressure in air funnel 80 as it draws air 97 from airfunnel 80, and creates a flow of warm convection air in air channelcavity 50 (sized to accommodate an air velocity of from about 400 toabout 700 feet per minute and to provide a heat displacement factor offrom about 2.2 to about 3.2 Watts per cubic inch, more particularly 2.75Watts per cubic inch) of base double cavity wall 48 as it forces air 97through heater 68. Air flow through air channel cavity 50 uniformlyheats base wall 47 of holding area 13 to a temperature of from about 150degrees F. to 180 degrees F. and base wall 47 radiates heat through foodholder 20 to warm food in food holder 20. Angled segments 98 of middlesection 44 of air outlet double cavity wall 41 maintain the laminar flowof air as the air accelerates (because air outlet air channel cavity 43,in one embodiment, is constricted relative to base air channel cavity50) upward 95 to air outlet port 91. Air outlet port 91 has from about20 to about 30 oval holes that promote laminar air flow, each holehaving a height of from about 1 to about 2 inches and a length of fromabout 0.15 to about 0.25 inches.

Angled segment 98 and optional air outlet port guiding bracket 89deflect a portion of the flow of warm convection air through air outletport 91 into holding area 13, in one embodiment at a downward angle offrom about 0 degrees to about 30 degrees (more particularly from about10 degrees to about 30 degrees), at a temperature of from about 225degrees F. to about 350 degrees F. (more particularly from about 190degrees F. to about 210 degrees F.), and at a velocity of from about 800to about 1200 feet per minute. The flowing air warms, and removesmoisture from, the surface of food (not shown) held in food holder 20.Undeflected air flowing through air outlet port 91, in one embodiment,across the top of food-holding area 13 and above food holder 20 (or inanother embodiment, air flowing along the side of holding area 13 and tothe side of food holder 20) as robust air curtain 61 removes moist airfrom holding area 13 and creates negative pressure through a Bernoullieffect that helps to evaporate moisture from the crisp food surface. Topwall 30 of holding area 13, by preventing upward extension of aircurtain 61, helps to maintain the laminar air flow, and to increase themoisture-evaporating Bernoulli effect, of air curtain 61. Thecombination of radiant heat, warm air convection, and warm air curtain61 and its resulting Bernoulli effect maintain a crisp food surface,internal food moisture, and a food temperature of from about 140 degreesF. to about 190 degrees F. Positive air pressure at air outlet port 91and negative air pressure at air inlet port 90 create and maintain thelaminar flow of air curtain 61. Air in holding area 13 exits holdingarea 13 by flowing through air inlet port 90 and air filter 99 into airfunnel 80. Angled side walls 84 of air funnel 80 promote laminar airflow as they guide warm flowing air 88 to opening 83 in base 81 of airfunnel 80. Extensions 82 of air funnel base 81 prevent unfiltered airfrom entering air blower 70.

Under adverse operating conditions (such as a blocked air port 90, 91),air blower 70 acts as a differential pressure switch to change thedirection of air flow so that the apparatus 10 continues to properlycondition food. Air blower 70 responds to greatly negative air pressurein air funnel 80 resulting from a blocked air inlet port 90 by drawing,through space 86 beneath extensions 82 of air funnel base 81, warm airfrom side cavity 39 instead of from air funnel 80. Air blower 70responds to greatly positive air pressure in air channel cavity 50 ofbase double cavity wall 48 resulting from blocked air outlet port 91 byblowing, through space 86 beneath extension 82 of air funnel base 81,warm air into side cavity 39 instead of into air channel cavity 50.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

What is claimed is:
 1. A method for maintaining the freshly cookedtexture and internal moisture of cooked food at temperatures from about140 degrees F. to about 190 degrees F. for at least two hours to providea biologically safe noncooking temperature, comprising the steps of:holding the food in an apparatus; generating within the apparatus a flowof recirculating convection air, the recirculating convection air beingheated to about 225 degrees F. to about 350 degrees F. and flowing at avelocity of from about 250 feet per minute to about 800 feet per minute;radiating heat to the food; applying the recirculating convection aironto and about the food; and generating from the recirculatingconvection air an air curtain of flowing air apart from the food andenveloping the food in an area of negative pressure that removes excessmoisture from the outer surface of the food.
 2. The method of claim 1,wherein the recirculating convection air flowing within a cavity of theappliance below the food has a velocity of from about 250 feet perminute to about 600 feet per minute; and the recirculating convectionair applied onto and about the food is heated to from about 265 degreesF. to about 325 degrees F.
 3. The method of claim 1, wherein theapparatus comprises an internally positioned blower, and an internallypositioned heater connected to the blower for heating flowing airreceived from the blower, the heater having a heat output of from about200 Watts to about 800 Watts, further comprising the step ofcontinuously supplying a constant amount of electrical power to theblower and to the heater, without any thermostatic control of the power.4. The method of claim 3, wherein the apparatus comprises an air inletfor supplying substantially all air to the blower under standardoperating conditions, further comprising the step of preventing the airinlet from supplying air to the blower.
 5. The method of claim 3,wherein the apparatus comprises an air outlet for exhaustingsubstantially all air from the blower under standard operatingconditions, further comprising the step of preventing the air outletfrom exhausting air from the blower.
 6. The method of claim 1, whereinthe radiating heat is below the food and is generated with a combinationof recirculating convection air flowing within a cavity and aninternally positioned heater located within the cavity.
 7. The method ofclaim 1, wherein the radiating heat is below the food is generatedsolely with an internally positioned heater located below the food. 8.The method of claim 1, wherein the air curtain of coherent flowing airis flowing directly over the food generating an area of negativepressure that removes excess moisture from the outer surface of thefood.
 9. The method of claim 1, wherein the radiating heat to the foodis generated with the recirculating convection air flowing within acavity located below the food.
 10. A method for maintaining the freshlycooked texture and internal moisture of cooked food for at least twohours at a biologically safe noncooking temperature in the range ofabout 140 degrees F. to about 190 degrees F., comprising the steps of:holding the food in an apparatus; generating within the apparatus a flowof recirculating convection air; heated to from about 225 degrees F. toabout 350 degrees F. and flowing at a velocity of from about 250 feetper minute to about 1500 feet per minute, onto and about the food;generating from the recirculating convection air an air curtain ofcoherent flowing air apart from the food and enveloping the food in anarea of negative pressure that removes excess moisture from the outersurface of the food.
 11. The method of claim 10, wherein therecirculating convection air applied onto and about the food is heatedto from about 265 degrees F. to about 325 degrees F. and has a velocityof from about 250 feet per minute to about 800 feet per minute.
 12. Amethod of maintaining the condition of cooked food, comprising: placingcooked food in a holding portion within an apparatus; radiating heatfrom the holding portion to the food within the apparatus; andgenerating an air curtain of coherent flowing air within the apparatusapart from the food and creating an area of negative air pressure toremove excess moisture from the surface of the food, wherein the aircurtain of coherent flowing air is from about 225 degrees F. to about350 degrees F. and flowing at a velocity of about 250 feet per minute toabout 150 feet per minute; wherein the radiating heat and the warm aircurtain of coherent flowing air maintain the cooked food at abiologically safe noncooking temperature in the range of about 140degrees F. to about 190 degrees F.
 13. The method of claim 12, whereinthe radiating heat is generated by heated convection air flowing withina cavity of the apparatus below the holding portion.
 14. The method ofclaim 13, wherein the heated convection air flowing within the cavitymoves at a velocity of about 250 feet per minute to about 800 feet perminute.
 15. The method of claim 12, wherein the holding portion includesa heating element for generating radiant heat.
 16. The method of claim15, wherein the heated convection air flowing within a cavity of theapparatus below the holding portion generates additional radiant heat.17. The method of claim 12, wherein the air curtain of coherent flowingair is generated by a blower and a heating element positioned within theapparatus.
 18. The method of claim 17, wherein the apparatus furthercomprises an air inlet for selectively supplying air from outside theapparatus to the blower and an air outlet for selectively venting airfrom the apparatus.
 19. The method of claim 12, wherein the area ofnegative air pressure is generated by selectively venting air from theapparatus.